McCulloch 4-cylindergas military drone engine, opposed 4-cylinder McCulloch 4381a 100-1 engine. TheMcCulloch Model 4318 (Military designation: O-100) was originally used as adrone engine.Two-stroke,4-cylinder opposed, 72 HP @ 4,100 rpm 3.1875"(81 mm) bore, 3.125" (79.4 mm) stroke, 99.7 in³ (1,635 cc) displacement,weight approximately 78 lbs (35.4 kg)Chrome-platedaluminum bore, pistons probably deflector type (as opposed to Schnurleloop-scavenged), single ignition Cool little engine! 72 HP, 75 pounds. BensenGyrocopters were designed around those engines. I have four of these . One complete engine came of my airplane, itis complete, I do have the manual for these engines. One engine has a broken mount. One in the box newly done. I guess you can say two good engines and two parts engines. I can help with the shipping but it is your responsibility cost and handling. Auctionis for all four engines. Current date: 2020-02-15